Huge explosions on the sun release a tremendous amount of energy and also quite a bit of mass out into space, says Mary Hudson, Professor and Chair of Physics and Astronomy. You have this mass at high velocity coming at the earth, with high energy, and that energy gets transferred to our smaller region of space.
Hudson is one of the principal investigators with the Center for Integrated Space Weather Modeling (CISM), a science and technology center funded by the National Science Foundation. Researchers with CISM, a multi-organizational effort administered through Boston University, study the weather patterns that originate from a solar eruption, following the energy through the interplanetary medium all the way to earth. Like a boulder subjected to rushing water in a spring creek, the earth endures an unending onslaught of solar wind, a stream of ionized particles and plasma released from the sun. Hurricanes in the solar wind, big solar eruptions, can wreak havoc with activities on earth, causing power surges and outages, triggering malfunctions with communications and weather satellites, and disrupting global positioning system equipment.
Mary Hudson and her colleagues, William Lotko (left) and John Lyon (center), want to find better ways to predict storms in space
Researchers track the progress of the solar wind toward earth in order to alert satellite companies, electric power corporations and even airlines. It usually takes about two days for the energy and mass released from the sun to get to earth, although some powerful events, like solar flares and coronal mass ejections, travel faster. Operators of technological systems use advance warning so they can adjust satellite command schedules, distribute the load on power transmission lines, or alter an airline route that might be affected by communications blackouts or increased radiation.
Scientists know quite a bit about space weather, but some particulars are still sketchy, so forecasting is based primarily on past experience rather than predictive models. Its the difference between saying that it will snow today and saying that it will start snowing at noon, accumulate four inches, taper off by dinner time, and the temperature will drop throughout the day, explains Hudson.
We want to be able to predict space weather, much like our colleagues who work in the meteorological community predict the earths weather, she says.
The heart of CISM lies in developing models that will accurately predict space weathers subtle effects on the earths near space environment. The Dartmouth component of CISM, which includes both Physics and Astronomy Department experts and colleagues at the Thayer School of Engineering, focuses on the magnetosphere, located above the ionosphere, the outmost layer of the earths atmosphere.
The earths magnetic field, which gives the magnetosphere its shape, provides a shield around our planet. Its not quite a complete bubble, however, but more of a bubble with a tail. Energy from the sun hits this bubble, and while some particles are swept aside and around the earth, some charged particles leak into the magnetosphere down into the ionosphere and directly to earth. This complex area between the outer magnetosphere and the polar regions where the earths magnetic field opens up is a place where charged particles, magnetic fields and electrical currents follow patterns that arent yet fully understood.
Hudsons group includes a team of professors, postdoctoral researchers, graduate students and undergraduates.
Current areas of investigation include:
- the evolution of radiation belts
- how the magnetic field of the sun interacts with the magnetic field of the earth
- electrical currents in the ionosphere
- the effect of cosmic rays, which are pushed by the solar wind into our atmosphere, on radio communications near the earths poles
These initiatives are all rooted in a mathematical code developed more than 10 years ago by John Lyon, Research Professor of Physics and Astronomy.
John developed one of a handful of 3-D codes for modeling the near earth space environment as a magnetized fluid, and for modeling the interactions of solar wind with that environment, says Hudson. That code is the backbone for modeling what happens inside the magnetosphere.
Like a boulder subjected to rushing water in a spring creek, the earth endures an unending onslaught of solar wind. (image courtesy of NASA/National Space Science and Technology Center)
With this code as the foundation for Dartmouths CISM projects, Hudsons group is taking a physics approach to modeling the space weather chain of events in the magnetosphere.
William Lotkos research involves connecting one of the missing links in the CISM chain. Lotko, a Professor of Engineering and the Acting Dean at the Thayer School of Engineering, studies one particularly complex sequence in the space weather route: the interchange between the magnetosphere and the ionosphere. This interaction, called magnetosphere-ionosphere coupling, involves electromagnetic power and mass transitions from the magnetosphere into the ionosphere. The ionosphere reacts by heating up, explains Lotko.
Theres a feedback effect, he says. The heated ionosphere sends mass back into the magnetosphere, and that changes the whole state of the magnetosphere. So you get this feedback loop; its not a one-way thing. One of the most significant two-way coupling problems to figure out in the whole CISM chain from the sun to the earth is that interaction.
Lotko says its a region rich for theorists to model. Because the plasma processes happen at small scales in magnetosphere-ionosphere coupling, the current large scale models dont take them into consideration. Lotko works to adjust the code to develop more accurate models.
We know that the small scale effects figure into the large scale dynamics and influence the overall behavior of the code, he says. Theres also the reversein which large scale phenomena regulate the small scale phenomena. Not only is there a coupling between the magnetosphere and the ionosphere, but theres a coupling across spatial spheres, from small to large and from large to small. Trying to describe that coupling across scales is something we have to do if were going to get the physics right and build good space weather models.
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